21811087 has 2 divisors, whose sum is σ = 21811088. Its totient is φ = 21811086.

The previous prime is 21811081. The next prime is 21811109. The reversal of 21811087 is 78011812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21811087 - 2³ = 21811079 is a prime.

It is a super-2 number, since 2×21811087² = 951447032243138, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21811081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10905543 + 10905544.

It is an arithmetic number, because the mean of its divisors is an integer number (10905544).

Almost surely, 2^21811087 is an apocalyptic number.

21811087 is a deficient number, since it is larger than the sum of its proper divisors (1).

21811087 is an equidigital number, since it uses as much as digits as its factorization.

21811087 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 21811087 is about 4670.2341483056. The cubic root of 21811087 is about 279.3995935655.

Adding to 21811087 its reverse (78011812), we get a palindrome (99822899).

The spelling of 21811087 in words is "twenty-one million, eight hundred eleven thousand, eighty-seven".